Cardiac thrombus is a blood clot formed within the cardiac chambers, most commonly seen at the left ventricular apex (post-myocardial infarction — 15-25% in anterior MI, particularly in akinetic/dyskinetic apex segments) or in the left atrial appendage (atrial fibrillation — in 10-15% of AF patients). Right heart thrombi are less common and typically appear as transit thrombus associated with deep vein thrombosis (DVT) or thrombus related to indwelling catheters/pacemaker leads. Cardiac thrombus has significant clinical importance — left heart thrombi carry risk of systemic embolization (stroke, peripheral arterial embolism), right heart thrombi can be a source of pulmonary embolism. Cardiac MR (CMR) is the gold standard for diagnosis — absence of enhancement on LGE sequences (avascular structure) is pathognomonic for differentiation from tumor. Echocardiography is the first-line imaging but has limited sensitivity particularly for left atrial appendage thrombus (TTE 33-60%, TEE 95-100%). Treatment is anticoagulation; surgical thrombectomy may be considered in cases with high embolization risk or resistance to anticoagulation.
Age Range
30-85
Peak Age
65
Gender
Equal
Prevalence
Common
Cardiac thrombus formation is based on Virchow's triad: (1) stasis — slowing of blood flow in akinetic/dyskinetic myocardial segments (post-MI) or in the dilated, irregularly contracting atrium in atrial fibrillation, (2) endothelial injury — necrotic endocardium after myocardial infarction, catheter trauma, or inflammation, (3) hypercoagulability — systemic procoagulant state. In left ventricular thrombus, apex segments are the most commonly affected areas after anterior MI because the LAD artery territory includes the apex and large anterior MI creates akinesis/dyskinesis at the apex — stagnant blood clots in this area. Left atrial appendage thrombus forms in atrial fibrillation because the atrium contracts irregularly in AF and blood flow in the appendage slows (the appendage is narrow, trabeculated, and prone to stasis). Thrombus organizes over time — acute thrombus is soft, homogeneous, and mobile; chronic thrombus becomes organized, may calcify, and is covered by endothelium. Basis of imaging findings: thrombus is an avascular structure — it contains no viable cells or neovascular structures, therefore does not take up contrast and remains dark on LGE. This characteristic is the physical basis for differentiation from tumor mass. On echocardiography, thrombus generally shows different echogenicity from myocardium and is located in areas with wall motion abnormality.
Complete absence of enhancement of an intracardiac mass on cardiac MR LGE sequences is a pathognomonic finding for cardiac thrombus diagnosis. Thrombus is an avascular structure — it contains neither neovascular vessels nor cellular uptake mechanism and gadolinium cannot reach inside the thrombus. This characteristic allows differentiation from tumors with >99% specificity because nearly all cardiac tumors (primary or metastatic) show some degree of LGE enhancement. Detection rate further increases with long TI (600+ ms) investigation sequences.
On LGE sequences, cardiac thrombus shows complete absence of enhancement — this finding is pathognomonic for thrombus diagnosis and the strongest criterion for differentiation from tumor. The myocardium surrounding the thrombus shows LGE-positive infarct area (subendocardial or transmural delayed enhancement). Small or organized thrombi are more difficult to detect on LGE — detection rate improves with long TI (600+ ms) inversion recovery or dedicated 'thrombus-detection' sequences. Sensitivity is 82-88% (compared to TTE 33-60%), and specificity has been reported above 99%.
Report Sentence
On LGE images, a non-enhancing mass measuring ___ cm at the left ventricular apex / left atrial appendage is seen, consistent with thrombus.
On T1-weighted images, thrombus signal varies depending on clot age. Acute thrombus (<1 week) appears iso- or slightly hyperintense due to deoxyhemoglobin. Subacute thrombus (1-4 weeks) shows marked T1 hyperintensity due to methemoglobin content. Chronic thrombus (>4 weeks) becomes organized and shows signal similar to myocardium — iso-hypointense with fibrosis and hemosiderin deposition. T1 signal helps in thrombus aging but is not as powerful as LGE for differential diagnosis.
Report Sentence
On T1-weighted images, a mass of ___ intensity and ___ cm size at ___ location is seen, with signal characteristics consistent with ___ stage thrombus.
On T2-weighted images, acute thrombus appears hypointense due to deoxyhemoglobin. Subacute thrombus appears T2 hypointense in intracellular methemoglobin stage and T2 hyperintense in extracellular methemoglobin stage. Chronic thrombus is markedly hypointense due to hemosiderin and fibrosis. T2 hypointensity is more prominent particularly with SWI/T2* sequences — susceptibility effect of hemosiderin. T2 may help in thrombus-tumor differentiation as tumors generally appear T2 hyperintense while thrombus is typically hypointense.
Report Sentence
On T2-weighted images, the mass at ___ location shows hypointense signal, consistent with thrombus containing hemoglobin degradation products.
On transthoracic echocardiography (TTE), left ventricular thrombus typically appears as a well-defined, echo-lucent or echogenic mass at the LV apex, attached to an akinetic or dyskinetic wall segment. Acute thrombus is usually echo-lucent and mobile — embolization risk is higher. Chronic thrombus is more echogenic, immobile, and has a laminated appearance. Left atrial appendage (LAA) thrombus cannot be reliably evaluated by TTE (sensitivity 33-60%) — TEE is required. On TEE, LAA thrombus appears as a hypo-/iso-echogenic mass within the appendage. Spontaneous echo contrast (SEC — 'smoke') in the LAA indicates stasis and thrombus risk. In right heart thrombus, transit thrombus may appear serpentine and mobile.
Report Sentence
On echocardiography, a mass measuring ___ cm at the left ventricular apex / left atrial appendage, attached to an akinetic wall segment, is seen, consistent with ___ thrombus.
On ECG-gated contrast-enhanced CT, cardiac thrombus appears as a hypoattenuating filling defect on delayed phase (60-90 sec). Thrombus does not take up contrast and is lower density than contrast-enhanced blood in the LV cavity. False positive results may occur in early phase as slow-flowing blood can also appear hypoattenuating — therefore delayed imaging is preferred. On CT angiography, LAA thrombus appears as a filling defect but slow-flow artifact (pseudo-thrombus) is in the differential — if filling occurs on delayed phase, thrombus is excluded. Calcified chronic thrombus shows high attenuation on CT.
Report Sentence
On delayed phase ECG-gated CT, a non-enhancing hypoattenuating filling defect measuring ___ cm at the left ventricular apex / left atrial appendage is seen, consistent with thrombus.
On color Doppler echocardiography, no blood flow is detected within the thrombus — thrombus is an avascular structure. This finding helps differentiate from tumor mass as vascularized tumors generally show internal flow. Slow flow or spontaneous echo contrast (SEC) may be observed in the cavity around the thrombus. Pulse-wave Doppler can evaluate the flow profile near the thrombus — low velocity flow is detected in stasis areas. In LAA evaluation with TEE, flow velocity within the appendage can be measured — low LAA flow velocity (<20 cm/s) is predictive for thrombus risk.
Report Sentence
On color Doppler evaluation, no flow signal is detected within the mass, findings consistent with avascular thrombus; spontaneous echo contrast is observed in the cavity.
Criteria
At LV apex, usually attached to post-MI akinetic/dyskinetic segment; most common after anterior MI
Distinct Features
Anterior MI history, apical akinesis/dyskinesis, low EF (<35%), systemic embolization risk (stroke) — acute thrombus mobile and emboli-prone, chronic thrombus organized and laminated
Criteria
Filling defect within LAA; associated with atrial fibrillation or mitral stenosis
Distinct Features
Diagnosis with TEE (TTE insufficient), LAA flow velocity <20 cm/s predictive, spontaneous echo contrast accompanies, cardioembolic stroke main risk, CHA2DS2-VASc score stratification
Criteria
Within right atrium or ventricle, usually DVT-sourced, transient or fixed thrombus
Distinct Features
Serpentine, mobile appearance (transit thrombus), DVT history, pulmonary embolism main risk, right heart failure, may be catheter/pacemaker related
Distinguishing Feature
Metastasis shows heterogeneous enhancement on LGE (neovascular structure), thrombus shows complete absence of enhancement (avascular). Metastases are usually multiple, thrombus is solitary. Metastasis has a known primary malignancy history.
Distinguishing Feature
Myxoma is a mobile, enhancing mass attached to the interatrial septum by a stalk — LGE positive. Thrombus shows no enhancement. Myxoma is typically in the left atrium while LV thrombus is at the apex. Myxoma is markedly T2 hyperintense.
Distinguishing Feature
Vegetation is a small (<2 cm), mobile, irregularly marginated mass attached to valve leaflet. Thrombus is usually attached to myocardial wall and not located on valve leaflets. In vegetation, fever, positive blood culture, and embolic events provide clinical foreground.
Distinguishing Feature
Papillary fibroelastoma is a small (<15 mm), pedunculated, mobile mass attached to valve surface — usually aortic or mitral valve. Thrombus is attached to wall segment. Fibroelastoma is typically incidentally detected and has benign histology despite carrying embolization risk.
Urgency
urgentManagement
medicalBiopsy
Not NeededFollow-up
3-monthWhen cardiac thrombus is diagnosed, anticoagulant therapy should be initiated and embolization risk assessed. For left ventricular thrombus, warfarin or DOAC (NOAC) therapy is recommended — duration is typically 3-6 months with follow-up imaging to evaluate thrombus resolution. Mobile, pedunculated, or large thrombi have higher embolization risk and surgical thrombectomy may be considered. When LAA thrombus is detected, cardioversion should be deferred, anticoagulant therapy initiated, and thrombus resolution confirmed by repeat TEE at 3-4 weeks. CHA2DS2-VASc score guides long-term anticoagulation decision. Right heart transit thrombus may require more aggressive approach due to acute pulmonary embolism risk. Biopsy is CONTRAINDICATED — thrombus mobilization and embolization risk. Follow-up imaging at 3 months — thrombus resolution is evaluated.
Cardiac thrombus is one of the most important causes of systemic embolization (stroke, mesenteric ischemia, peripheral arterial occlusion). Anticoagulation therapy (heparin → warfarin/DOAC) is essential. LV thrombus typically develops after anterior MI and 3-6 months of anticoagulation is recommended. Left atrial thrombus must be excluded before cardioversion in AF patients (via TEE). Mobile and pedunculated thrombi may require surgical removal.